Hallux valgus is characterized as a deformity of the great toe (hallux) and first metatarsophalangeal joint, wherein the first metatarsal is medially deviated, the great toe is laterally deviated and/or rotated on the head of the metatarsal, the plantar pad and sesamoids are displaced with the toe, and the ligaments on the medial side of the metatarsophalangeal joint are stretched. The position of the great toe with respect to the second toe can be overriding, underriding, abutting, or without contact. Thus, hallux valgus can involve transverse plane deformities (hallux abductus), or frontal and transverse plane deformities (hallux abductovalgus). With respect to deformities in the transverse plane, the angle between the longitudinal axis of the metatarsals of the first and second toes (intermetatarsal angle) typically deviates beyond the normal range of 8-12°. With respect to deformities in the frontal plane, the angle between the longitudinal axis of the metatarsal and proximal phalanx of the great toe (hallux valgus angle) typically deviates beyond the normal upper limit of 15-20°.
In addition to physical deformity, hallux valgus is often accompanied by formation of a callous, bursa, or bunion over the first metatarsal head, pain in the first metatarsophalangeal joint during ambulation, pain in the metatarsal head, and combinations thereof.
Hallux valgus is estimated to affect more than 43 million people in the United States, with incidence more predominate in females, those older than 60 years of age, teenagers who wear high heels, and athletes. It can develop due to numerous factors, including biomechanical instability (e.g., excessive protonation), arthritic/metabolic conditions (e.g., osteo/rheumatoid arthritis), neuromuscular disease (e.g., multiple sclerosis), trauma (e.g., soft-tissue sprains, dislocations, and sports-related injuries), and structural deformities (e.g., abnormal metatarsal length). Additionally, there tends to be familial disposition to developing hallux valgus.
Development of hallux valgus typically occurs in four stages. See Root, ML, “Normal and Abnormal Function of the Foot,” Vol. 2, Clinical Biomechanics (1977). The first stage is associated with lateral subluxation (partial or complete dislocation) of the proximal phalanx. The second stage is associated with increased abduction of the hallux in the transverse and/or frontal planes. The third stage is associated with additional subluxation at the first metatarsophalangeal joint. The fourth stage is associated with dislocation of the first metatarsophalangeal joint.
Hallux valgus is a complex deformity and various approaches to treating or correcting the deformity may be available. For example, surgery is the only means of correcting the deformity and when hallux valgus is in its later stages, surgery may be the only means of treatment. However, when hallux valgus is in its early stages, or where surgical correction is contraindicated, braces, straps, splints, orthotics, or combinations thereof may be used to manage progression of the deformity and relieve the associated symptoms.
Because braces, straps, splints, and orthotics are non-invasive, cost-effective, and may be self-applied, they represent important means of treating hallux valgus. Such devices are typically designed to relieve the symptoms of the deformity by attempting to reduce the intermetatarsal angle, realign the hallux to a rectus (rather than an abductus) position, or combinations thereof by applying force to various portions of the foot. Braces, straps, splints, and orthotics may also be used for post-operative wear to maintain appropriate alignment during the healing process, to prevent recurrence, or both.
Conventional non-surgical treatment devices have numerous disadvantages, including bulkiness, difficulty in wearing in shoes, requiring periodic readjustment, creation of undesired pressure and irritation, complexity of application, and failure to relieve the deformity. Accordingly, there is need in the art for improved non-surgical devices for use in treating hallux valgus.